Opening/closing chuck and method of manufacturing fingers

ABSTRACT

A finger includes a pair of overhanging portions that project out laterally from a main body portion. Outer peripheral surfaces of the overhanging portions are made up from five surfaces including upper surfaces, side surfaces, lower surfaces, first end surfaces, and second end surfaces. Crowning is applied to the intersections between these surfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2021-023916 filed on Feb. 18, 2021, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an opening/closing chuck equipped witha pair of fingers for gripping a workpiece, as well as a method formanufacturing the fingers.

Description of the Related Art

Conventionally, an opening/closing chuck has been known in which a pairof fingers for gripping a workpiece are slidably supported in directionsto approach and separate away from each other. For example, in JP2003-526528 A, a parallel gripper is disclosed which adjusts awedge-shaped hook transmission portion by a piston. The wedge-shapedhook transmission portion brings two base jaws, which are movably guidedin a housing, into closer proximity or farther away from each other.

Further, in EP 3563989 A1, in a grip device equipped with a pair ofslides, it is disclosed that ramps are provided on guide flanks of therespective slides. In accordance therewith, a wedge gap is formed thatwidens toward end surfaces of the slides.

SUMMARY OF THE INVENTION

When a workpiece is gripped using a pair of slidably supported fingers,due to a reaction force from the workpiece, a load in a predetermineddirection (a vertical direction or a lateral direction) acts on thefingers. Further, moments act which attempt to rotate the fingers aboutvarious three-dimensional axes. The loads and the moments that act onthe fingers increase as the gripping force on the workpiece increases.Further, the moments that act on the fingers increase as the distancebetween workpiece gripping positions on gripping members (attachments),which are provided to extend from the fingers, and the supportedpositions of the fingers become longer. When such loads or momentsacting on the fingers are large, concentration of stress occurs oncontact surfaces between the fingers and the body, excessive surfacepressure is generated, and the fingers and the sliding surfaces of thebody are damaged.

However, a technique that takes into consideration concentration ofstress generated in the fingers and the body has not yet beensufficiently developed. The technique disclosed in EP 3563989 A1 issomewhat effective in relieving concentration of stress and preventingexcessive surface pressure when opposing ends of a pair of slidesattempt to rotate so as to open at an angle. However, the disclosedtechnique does not take into consideration that variousthree-dimensional axial moments act on the slides.

The present invention has the object of solving the aforementionedproblem.

An opening/closing chuck according to the present invention comprises apair of fingers configured to slide inside of a guide groove of a body,and which are slidably supported in directions to approach toward andseparate away from each other. The fingers each include a pair ofoverhanging portions configured to project out laterally from a mainbody portion, and outer peripheral surfaces of the overhanging portionsare made up from five surfaces including upper surfaces, side surfaces,lower surfaces, first end surfaces, and second end surfaces. Crowning isapplied to intersections between these surfaces.

According to the above-described opening/closing chuck, concentration ofstress generated in the fingers due to loads acting on the fingers in avertical direction and moments about three axes can be alleviated, and amaximum surface pressure can be lowered.

Further, in a first method of manufacturing according to the presentinvention, the fingers slide inside a guide groove of a body of anopening/closing chuck, are slidably supported in directions to approachtoward and separate away from each other, and include a pair ofoverhanging portions configured to project out laterally from a mainbody portion. Outer peripheral surfaces of the overhanging portions aremade up from five surfaces including upper surfaces, side surfaces,lower surfaces, first end surfaces, and second end surfaces, wherein theupper and lower surfaces are perpendicular to the side surfaces. Thefirst method of manufacturing comprises a step of applying crowning atintersections of the five surfaces, by a combination of performinggrinding with respect to the side surfaces by a first machining tool,and performing grinding with respect to the upper surfaces and the lowersurfaces by a second machining tool.

Further, in a second method of manufacturing according to the presentinvention, the fingers slide inside a guide groove of a body of anopening/closing chuck, are slidably supported in directions to approachtoward and separate away from each other, and include a pair ofoverhanging portions configured to project out laterally from a mainbody portion. Outer peripheral surfaces of the overhanging portions aremade up from five surfaces including upper surfaces, side surfaces,lower surfaces, first end surfaces, and second end surfaces, and theupper surfaces and the lower surfaces are tapered surfaces configured tocome into closer proximity to each other toward the side surfaces. Thesecond method of manufacturing comprises a step of applying crowning atintersections of the five surfaces, by performing grinding with respectto the side surfaces, and simultaneously performing grinding withrespect to the upper surfaces and the lower surfaces using a singlemachining tool.

According to the first method of manufacturing and the second method ofmanufacturing described above, the crowning process for alleviating theconcentration of stress generated in the fingers and the body can beeasily performed in a fewer number of steps. The above-describedconcentration of stress is caused by loads acting on the fingers in thevertical direction and moments about the three axes.

In the opening/closing chuck according to the present invention,crowning is applied to the intersections of the five surfaces includingthe upper surfaces, the side surfaces, the lower surfaces, the first endsurfaces, and the second end surfaces that make up the outer peripheralsurfaces of the overhanging portions of the fingers. Therefore, it ispossible to alleviate concentration of stress when moments about thethree axes or loads in a vertical direction act on the fingers.

Further, in the first method of manufacturing the fingers according tothe present invention, grinding with respect to the side surfaces of theoverhanging portions by the first machining tool, and grinding withrespect to the upper surfaces and the lower surfaces of the overhangingportions by the second machining tool are combined. Consequently, sincecrowning is applied to the intersections of the five surfaces of theoverhanging portions, the crowning process can be easily performed in afewer number of steps.

Further, in the second method of manufacturing the fingers according tothe present invention, using a single machining tool, grinding isperformed with respect to the side surfaces of the overhanging portionsand simultaneously grinding is performed with respect to the uppersurfaces and the lower surfaces of the overhanging portions.Consequently, since crowning is applied to the intersections of the fivesurfaces of the overhanging portions, the crowning process can be easilyperformed in an even fewer number of steps.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings, in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an external perspective view of an opening/closing chuckaccording to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line II-II of theopening/closing chuck shown in FIG. 1;

FIG. 3 is a front view of the opening/closing chuck shown in FIG. 1;

FIG. 4 is an external perspective view of a finger of theopening/closing chuck shown in FIG. 1;

FIG. 5 is a diagram showing a portion of a cross section of a finger anda body taken along line V-V of FIG. 3;

FIG. 6A is an enlarged view of a portion A shown in FIG. 3;

FIG. 6B is an enlarged view of a portion B shown in FIG. 3;

FIG. 7 is a diagram schematically showing a method of applying crowningto the finger shown in FIG. 4;

FIG. 8 is a diagram schematically showing a path over which a firstmachining tool is made to move when crowning is applied to the fingershown in FIG. 4;

FIG. 9 is a diagram schematically showing a path over which a secondmachining tool is made to move when crowning is applied to the fingershown in FIG. 4;

FIG. 10 is a front view of an opening/closing chuck according to asecond embodiment of the present invention;

FIG. 11A is an enlarged view of a portion C shown in FIG. 10;

FIG. 11B is an enlarged view of a portion D shown in FIG. 10;

FIG. 12 is a diagram schematically showing a method of applying crowningto the finger shown in FIG. 10;

FIG. 13 is a diagram schematically showing a path over which a thirdmachining tool is made to move when crowning is applied to the finger ofthe opening/closing chuck shown in FIG. 10;

FIG. 14 is a perspective view of a finger of an opening/closing chuckaccording to a third embodiment of the present invention; and

FIG. 15 is a diagram schematically showing a path over which a thirdmachining tool is made to move when crowning is applied to the fingershown in FIG. 14.

DESCRIPTION OF THE INVENTION

In the description given below, when terms related to the up, down,left, and right directions are used, the terms refer to the directionsshown in the drawings for the sake of convenience, and such terms arenot intended to limit the actual arrangement or the like of therespective constituent members.

First Embodiment

A description will be given with reference to FIGS. 1 to 6 concerning anopening/closing chuck 10 according to the first embodiment of thepresent invention. As shown in FIGS. 1 and 2, the opening/closing chuck10 includes a rectangular parallelepiped shaped body 12, and a pair offingers 14 that are slidably supported in a longitudinal direction (theX direction) of the body 12. The opening/closing chuck 10 is used byconnecting non-illustrated attachments for gripping a workpiece to thefingers 14. That which is shown by reference numeral 14 a are screwholes used for connecting the attachments.

The body 12 includes a cylinder chamber 24 at a lower central part inthe longitudinal direction. Further, the body 12 has a guide groove 22that extends in the longitudinal direction of the body 12, and both endsof which open on end surfaces of the body 12 at portions above thecylinder chamber 24. A piston 26 which is capable of sliding in avertical direction (Z direction) is disposed in the cylinder chamber 24.The cylinder chamber 24 is partitioned into a first pressure chamber 24a formed on a lower side of the piston 26, and a second pressure chamber24 b formed on an upper side of the piston 26. The first pressurechamber 24 a is closed by a cap 30.

A piston rod 28 which is connected by a bolt 32 to the piston 26 extendsfurther upward through the second pressure chamber 24 b. An upper partof the piston rod 28 faces toward the guide groove 22 and constitutes acam portion 28 a of a known structure for driving the fingers 14. Whenair is supplied to the first pressure chamber 24 a and the air in thesecond pressure chamber 24 b is discharged, the piston 26 and the pistonrod 28 are moved upward. Consequently, the pair of fingers 14 slide indirections away from each other. When air is supplied to the secondpressure chamber 24 b and the air in the first pressure chamber 24 a isdischarged, the piston 26 and the piston rod 28 are moved downward.Consequently, the pair of fingers 14 slide in directions to approach oneanother.

As shown in FIG. 3 and FIG. 4, each of the fingers 14 has an invertedT-shaped cross section. Each of the fingers 14 includes a pair ofoverhanging portions 16 and 18 that project out laterally from the mainbody portion 20 over the entire length in the longitudinal direction(the X direction) of the fingers 14. The guide groove 22 of the body 12has an inverted T-shaped cross section that conforms to thecross-sectional shape of the fingers 14. The fingers 14 slide whileundergoing sliding movement inside the guide groove 22 of the body 12.

In order to enable the sliding movement of the fingers 14, uppersurfaces 16 a and 18 a, side surfaces 16 b and 18 b, and lower surfaces16 c and 18 c of the overhanging portions 16 and 18 face toward the wallsurface of the guide groove 22 with a minute gap therebetween. A gapwhich is larger than the aforementioned minute gap exists between theside surfaces 20 a and 20 b of the main body portion 20 and the wallsurfaces of the guide groove 22.

The bottom surface 20 c of the main body portion 20 lies substantiallyflush with the lower surfaces 16 c and 18 c of the overhanging portions16 and 18. Stepped portions 22 a exists between the wall surface of theguide groove 22 facing toward the bottom surface 20 c of the main bodyportion 20, and the wall surfaces of the guide groove 22 facing towardthe lower surfaces 16 c and 18 c of the overhanging portions 16 and 18(see FIG. 6B).

Outer peripheral surfaces of the respective overhanging portions 16 and18 of the fingers 14 are made up from five surfaces including the uppersurfaces 16 a and 18 a, the side surfaces 16 b and 18 b, the lowersurfaces 16 c and 18 c, first end surfaces (end surfaces in thedirection X1) 16 d and 18 d, and second end surfaces (end surfaces inthe direction X2) 16 e and 18 e. The upper surfaces 16 a and 18 a andthe lower surfaces 16 c and 18 c of the respective overhanging portions16 and 18 are perpendicular to the side surfaces 20 a and 20 b of themain body portion 20, and are perpendicular to the side surfaces 16 band 18 b of the overhanging portions 16 and 18.

Crowning is applied to the intersections between the above-describedfive surfaces. More specifically, crowning is applied to theintersections between the upper surfaces 16 a and 18 a and the first endsurfaces 16 d and 18 d, to the intersections between the side surfaces16 b and 18 b and the first end surfaces 16 d and 18 d, and to theintersections between the lower surfaces 16 c and 18 c and the first endsurfaces 16 d and 18 d. Similarly, crowning is applied to theintersections between the upper surfaces 16 a and 18 a and the secondend surfaces 16 e and 18 e, to the intersections between the sidesurfaces 16 b and 18 b and the second end surfaces 16 e and 18 e, and tothe intersections between the lower surfaces 16 c and 18 c and thesecond end surfaces 16 e and 18 e. Further, crowning is also applied tothe intersections between the upper surfaces 16 a and 18 a and the sidesurfaces 16 b and 18 b, and to the intersections between the lowersurfaces 16 c and 18 c and the side surfaces 16 b and 18 b.

In these crownings, gaps are formed between the overhanging portions 16and 18 of the fingers 14 and the wall surfaces of the guide groove 22,in a manner so as to continuously and gently expand from portions whereboth members are in contact. In this instance, the meaning of “gaps areformed in a manner so as to continuously and gently expand from portionswhere both members are in contact” is supplemented as follows (the sameapplies to other locations of the same description given in the presentspecification). When the fingers are placed in contact with the bodyunder a strong pressure, one or both of the fingers and the body areelastically deformed, and the boundary between the regions where bothmembers are in contact and the regions where they are not in contact ismoved. Crowning is applied to a region including from a starting pointof the boundary to a conceivable end point, and is formed so as to drawa gentle curve across the entire region. More specifically, it isnecessary to prevent locations from being generated where angles(corners) are formed in the regions where the fingers are placed incontact with the body. Crowning, which is applied to the intersectionbetween the first end surface 16 d and the lower surface 16 c of theoverhanging portion 16, is shown in FIG. 5. Crowning, which is appliedto the intersection between the side surface 16 b and the upper surface16 a of the overhanging portion 16, is shown in FIG. 6A. Crowning, whichis applied to the intersection between the side surface 16 b and thelower surface 16 c of the overhanging portion 16, is shown in FIG. 6B.

Further, in the guide groove 22 of the body 12, crowning is applied tothe intersections between the wall surfaces facing toward the uppersurfaces 16 a and 18 a of the overhanging portions 16 and 18 and thewall surfaces facing toward the side surfaces 20 a and 20 b of the mainbody portion 20. Furthermore, crowning is also applied to locationswhere the stepped portions 22 a face toward the lower surfaces 16 c and18 c of the overhanging portions 16 and 18.

In these crownings as well, gaps are formed between the overhangingportions 16 and 18 of the fingers 14 and the wall surfaces of the guidegroove 22, in a manner so as to continuously and gently expand fromportions where both members are in contact. Crowning, which is appliedto the intersection between the wall surface of the guide groove 22facing toward the upper surface 16 a of the overhanging portion 16 andthe wall surface of the guide groove 22 facing toward the side surface20 a of the main body portion 20, is shown in FIG. 6A. Crowning, whichis applied to a location where the stepped portion 22 a faces toward thelower surface 16 c of the overhanging portion 16, is shown in FIG. 6B.

When the workpiece is gripped using the opening/closing chuck 10, apitch moment (a moment about the Y axis) acts on the fingers 14.Further, there may be cases in which loads in the vertical direction (inthe Z direction), loads in the lateral direction (in the Y direction), aroll moment (a moment about the X axis), and a yaw moment (a momentabout the Z axis) act on the fingers 14.

The crowning applied to the intersections between the upper surfaces 16a and 18 a and the first end surfaces 16 d and 18 d, and to theintersections between the lower surfaces 16 c and 18 c and the first endsurfaces 16 d and 18 d alleviates concentration of stress primarily whena pitch moment acts on the fingers 14. The crowning applied to theintersections between the upper surfaces 16 a and 18 a and the secondend surfaces 16 e and 18 e, and to the intersections between the lowersurfaces 16 c and 18 c and the second end surfaces 16 e and 18 ealleviates concentration of stress primarily when a pitch moment acts onthe fingers 14. Assuming that the radius of curvature of these crowningsis indicated by R1, and the length of the overhanging portions 16 and 18in the longitudinal direction (the X direction) is indicated by L, thevalue of R1/L preferably lies within a range of 0.1 to 27.

The crowning applied to the intersections between the upper surfaces 16a and 18 a and the side surfaces 16 b and 18 b, and to the intersectionsbetween the lower surfaces 16 c and 18 c and the side surfaces 16 b and18 b alleviates concentration of stress primarily when a roll momentacts on the fingers 14. Assuming that the radius of curvature of thesecrownings is indicated by R2, and the length of the overhanging portions16 and 18 in the widthwise direction (the Y direction) is indicated byW, the value of R2/W preferably lies within a range of 0.1 to 27. Thecrowning applied to the guide groove 22 of the body 12 also alleviatesconcentration of stress when a roll moment acts on the fingers 14.

The crowning applied to the intersections between the side surfaces 16 band 18 b and the first end surfaces 16 d and 18 d, and to theintersections between the side surfaces 16 b and 18 b and the second endsurfaces 16 e and 18 e alleviates concentration of stress primarily whena yaw moment acts on the fingers 14. Assuming that the radius ofcurvature of these crownings is indicated by R3, and the length of theoverhanging portions 16 and 18 in the longitudinal direction isindicated by L, the value of R3/L preferably lies within a range of 0.1to 27.

The crowning applied to the intersections between the lower surfaces 16c and 18 c and the first end surfaces 16 d and 18 d alleviatesconcentration of stress when loads in the vertical direction act on thefingers 14. The crowning applied to the intersections between the lowersurfaces 16 c and 18 c and the second end surfaces 16 e and 18 e, and tothe intersections between the lower surfaces 16 c and 18 c and the sidesurfaces 16 b and 18 b also alleviates concentration of stress whenloads in the vertical direction act on the fingers 14. Among thecrowning applied to the guide groove 22 of the body 12, the crowningapplied to portions where the stepped portions 22 a face toward thelower surfaces 16 c and 18 c of the overhanging portions 16 and 18 alsoalleviates concentration of stress when loads in the vertical directionact on the fingers 14.

The crowning applied to the intersections between the side surfaces 16 band 18 b and the first end surfaces 16 d and 18 d alleviatesconcentration of stress when loads in the lateral direction act on thefingers 14. The crowning applied to the intersections between the sidesurfaces 16 b and 18 b and the second end surfaces 16 e and 18 e, to theintersections between the upper surfaces 16 a and 18 a and the sidesurfaces 16 b and 18 b, and to the intersections between the lowersurfaces 16 c and 18 c and the side surfaces 16 b and 18 b alsoalleviates concentration of stress when loads in the lateral directionact on the fingers 14.

In accordance with the opening/closing chuck 10 according to the presentembodiment, crowning is applied to the intersections between the fivesurfaces including the upper surfaces 16 a and 18 a, the side surfaces16 b and 18 b, the lower surfaces 16 c and 18 c, the first end surfaces16 d and 18 d, and the second end surfaces 16 e and 18 e that make upthe outer peripheral surfaces of the overhanging portions 16 and 18 ofthe fingers 14. Further, crowning is applied to a predetermined locationof the guide groove 22 of the body 12. Therefore, it is possible toalleviate concentration of stress when moments about the three axes orloads in a vertical direction act on the fingers 14.

Next, a description will be given with reference to FIGS. 7 to 9concerning a method of manufacturing the fingers 14 of theopening/closing chuck 10, and more specifically, concerning a method (acrowning process) of applying crowning to the fingers 14.

This crowning process involves application of all of the aforementionedcrownings, by a combination of performing grinding with respect to theside surfaces 16 b and 18 b of the pair of overhanging portions 16 and18, and performing grinding with respect to the upper surfaces 16 a and18 a and the lower surfaces 16 c and 18 c of the pair of overhangingportions 16 and 18. Grinding with respect to the side surfaces 16 b and18 b of the pair of overhanging portions 16 and 18 is performed using afirst machining tool 34 made up from a grindstone or an end mill.Grinding with respect to the upper surfaces 16 a and 18 a and the lowersurfaces 16 c and 18 c of the pair of overhanging portions 16 and 18 isperformed using a second machining tool 36 made up from a grindstone oran end mill.

As shown in FIG. 7, the first machining tool 34, which is a rotatingbody, is made so that the shape of a surface thereof, which is incontact with the workpiece to be machined, matches the shapes of theside surfaces 16 b and 18 b of the target overhanging portions 16 and18. The first machining tool 34 includes crowning machining portions 34a on both ends thereof. The first machining tool 34 is arranged so thatan axis thereof is arranged so as to be oriented along the Z direction,and can be rotationally driven about such an axis. Further, the firstmachining tool 34 is capable of being freely moved in the X directionand the Y direction. It should be noted that, in FIG. 7, one of thefingers 14 having a shape after the crowning process has been performedthereon is shown for the sake of convenience.

In the same manner, the second machining tool 36, which is a rotatingbody, is made so that the shape of a surface thereof, which is incontact with the workpiece to be machined, matches the shapes of theupper surfaces 16 a and 18 a and the lower surfaces 16 c and 18 c of thetarget overhanging portions 16 and 18. The second machining tool 36includes a crowning machining portion 36 a on one end thereof. Thesecond machining tool 36 is arranged so that an axis thereof is arrangedso as to be oriented along the Y direction, and can be rotationallydriven about such an axis. Further, the second machining tool 36 iscapable of being freely moved in the X direction and the Z direction.

When the crowning process is performed, first, the fingers 14 are fixedto a clamp base 38 in a posture with the pair of overhanging portions 16and 18 facing upward. At this time, the first machining tool 34 isplaced in a retracted position separated away from the side surface 16 bby a predetermined distance midway along the longitudinal direction (theX direction) of the side surface 16 b of one of the overhanging portions16. Further, the second machining tool 36 is placed in a retractedposition separated away from the lower surface 18 c by a predetermineddistance midway along the longitudinal direction (the X direction) ofthe lower surface 18 c of another of the overhanging portions 18.

Next, while being rotated about the axis thereof, the first machiningtool 34 is made to move in the Y2 direction and approach toward the sidesurface 16 b of the one of the overhanging portions 16, and is broughtinto contact at a predetermined pressure with the side surface 16 b. Inaccordance therewith, the side surface 16 b of the one of theoverhanging portions 16 at a site where the first machining tool 34 isplaced in contact therewith is subjected to grinding. In order toperform such grinding over the entire side surface 16 b of the one ofthe overhanging portions 16 and the entire side surface 18 b of theother of the overhanging portions 18, the first machining tool 34 ismade to move in a circling manner around the outer sides thereof.

More specifically, as schematically shown in FIG. 8, the first machiningtool 34 is made to move in the X1 direction along the side surface 16 bof the one of the overhanging portions 16 until arriving in the vicinityof the first end surface 16 d. Thereafter, the first machining tool 34is made to move in the Y2 direction until arriving in the vicinity ofthe side surface 18 b of the other of the overhanging portions 18 whileremaining at a distance from the finger 14, and furthermore, is made tomove in the X2 direction until arriving in the vicinity of the secondend surface 18 e along the side surface 18 b of the other of theoverhanging portions 18. Next, the first machining tool 34 is made tomove in the Y1 direction until arriving in the vicinity of the sidesurface 16 b of the one of the overhanging portions 16 while remainingat a distance from the finger 14, and thereafter, is made to move in theX1 direction along the side surface 16 b of the one of the overhangingportions 16 until being returned to its original position.

When the first machining tool 34 is moved, in order for crowning to beapplied to the intersection between the side surface 16 b and the firstend surface 16 d of the one of the overhanging portions 16, at theintersection, grinding is performed while controlling the amount oftraveling in the X1 direction and the amount of traveling in the Y2direction of the first machining tool 34 toward a target shape. Further,in order for crowning to be applied to the intersection between the sidesurface 18 b and the first end surface 18 d of the other of theoverhanging portions 18, at the intersection, grinding is performedwhile controlling the amount of traveling in the X2 direction and theamount of traveling in the Y2 direction of the first machining tool 34toward a target shape. Similarly, in order for crowning to be applied tothe intersection between the side surface 18 b and the second endsurface 18 e of the other of the overhanging portions 18, at theintersection, grinding is performed while controlling the amount oftraveling in the X2 direction and the amount of traveling in the Y1direction of the first machining tool 34 toward a target shape. Further,in order for crowning to be applied to the intersection between the sidesurface 16 b and the second end surface 16 e of the one of theoverhanging portions 16, at the intersection, grinding is performedwhile controlling the amount of traveling in the X1 direction and theamount of traveling in the Y1 direction of the first machining tool 34toward a target shape.

By causing the first machining tool 34 to circle one time therearound,grinding with respect to the side surfaces 16 b and 18 b of the pair ofoverhanging portions 16 and 18 is completed. Rotation of the firstmachining tool 34 is made to stop, and the first machining tool 34 isseparated and retracted away from the side surface 16 b of the one ofthe overhanging portions 16.

Next, while being rotated about the axis thereof, the second machiningtool 36 is made to move in the Z1 direction and approach toward thelower surface 18 c of the other of the overhanging portions 18, and isbrought into contact at a predetermined pressure with the lower surface18 c. In accordance therewith, the lower surface 18 c of the other ofthe overhanging portions 18 at a site where the second machining tool 36is placed in contact therewith is subjected to grinding. In order toperform such grinding over the entire lower surface 18 c and the entireupper surface 18 a of the other of the overhanging portions 18, thesecond machining tool 36 is made to move in a circling manner around theouter sides thereof.

More specifically, as schematically shown in FIG. 9, the secondmachining tool 36 is made to move in the X1 direction along the lowersurface 18 c of the other of the overhanging portions 18 until arrivingin the vicinity of the first end surface 18 d. Thereafter, the secondmachining tool 36 is made to move in the Z1 direction until arriving inthe vicinity of the upper surface 18 a while remaining at a distancefrom the finger 14. Furthermore, the second machining tool 36 is made tomove in the X2 direction along the upper surface 18 a until arriving inthe vicinity of the second end surface 18 e. Next, the second machiningtool 36 is made to move in the Z2 direction until arriving in thevicinity of the lower surface 18 c while remaining at a distance fromthe finger 14. Thereafter, the second machining tool 36 is made to movein the X1 direction along the lower surface 18 c until being returned toits original position.

When the above-described second machining tool 36 is moved, in order forcrowning to be applied to the intersection between the lower surface 18c and the first end surface 18 d, at the intersection, grinding isperformed while controlling the amount of traveling in the X1 directionand the amount of traveling in the Z1 direction of the second machiningtool 36 toward a target shape. Further, in order for crowning to beapplied to the intersection between the upper surface 18 a and the firstend surface 18 d, at the intersection, grinding is performed whilecontrolling the amount of traveling in the X2 direction and the amountof traveling in the Z1 direction of the second machining tool 36 towarda target shape. Further, in order for crowning to be applied to theintersection between the upper surface 18 a and the second end surface18 e, at the intersection, grinding is performed while controlling theamount of traveling in the X2 direction and the amount of traveling inthe Z2 direction of the second machining tool 36 toward a target shape.Further, in order for crowning to be applied to the intersection betweenthe lower surface 18 c and the second end surface 18 e, at theintersection, grinding is performed while controlling the amount oftraveling in the X1 direction and the amount of traveling in the Z2direction of the second machining tool 36 toward a target shape.

By causing the second machining tool 36 to circle one time around theother of the overhanging portions 18, grinding with respect to the uppersurface 18 a and the lower surface 18 c of the other of the overhangingportions 18 is completed. Rotation of the second machining tool 36 ismade to stop, and the second machining tool 36 is separated andretracted away from the lower surface 18 c of the other of theoverhanging portions 18.

Next, the clamp base 38 is rotated 180 degrees in the horizontal planeso that the second machining tool 36 is positioned in facing relation tothe lower surface 16 c of the one of the overhanging portions 16.Thereafter, while being rotated again about the axis thereof, the secondmachining tool 36 is made to move in the Z1 direction and approachtoward the lower surface 16 c of the one of the overhanging portions 16,and is brought into contact at a predetermined pressure with the lowersurface 16 c. In accordance therewith, the lower surface 16 c of the oneof the overhanging portions 16 at a site where the second machining tool36 is placed in contact therewith is subjected to grinding. In order toperform such grinding over the entire upper surface 16 a and the entirelower surface 16 c of the one of the overhanging portions 16, the secondmachining tool 36 is made to move in a circling manner around the outersides thereof.

More specifically, the second machining tool 36 is made to move in theX2 direction along the lower surface 16 c of the one of the overhangingportions 16 until arriving in the vicinity of the second end surface 16e. Thereafter, the second machining tool 36 is made to move in the Z1direction until arriving in the vicinity of the upper surface 16 a whileremaining at a distance from the finger 14. Furthermore, the secondmachining tool 36 is made to move in the X1 direction along the uppersurface 16 a until arriving in the vicinity of the first end surface 16d. Next, the second machining tool 36 is made to move in the Z2direction until arriving in the vicinity of the lower surface 16 c whileremaining at a distance from the finger 14. Thereafter, the secondmachining tool 36 is made to move in the X2 direction along the lowersurface 16 c until being returned to its original position.

When the second machining tool 36 is moved, the amount of traveling inthe X direction and the amount of traveling in the Z direction of thesecond machining tool 36 is controlled, in the same manner as in thecase of the other of the overhanging portions 18, at the intersectionbetween the lower surface 16 c and the second end surface 16 e, at theintersection between the upper surface 16 a and the second end surface16 e, at the intersection between the upper surface 16 a and the firstend surface 16 d, and at the intersection between the lower surface 16 cand the first end surface 16 d.

By causing the second machining tool 36 to circle one time around theone of the overhanging portions 16, grinding with respect to the uppersurface 16 a and the lower surface 16 c of the one of the overhangingportions 16 is completed. Rotation of the second machining tool 36 ismade to stop, and the second machining tool 36 is separated andretracted away from the lower surface 16 c of the one of the overhangingportions 16. Due to the steps described above, crowning can be appliedto the intersections of the five surfaces that make up the outerperipheral surfaces of the pair of overhanging portions 16 and 18 of thefingers 14.

Second Embodiment

Next, a description will be given with reference to FIGS. 10 to 13concerning a method of manufacturing an opening/closing chuck 40 andfingers 42 thereof according to a second embodiment of the presentinvention. In the opening/closing chuck 40 according to the secondembodiment, the shape of the pair of overhanging portions of the fingersand the shape of the guide groove of the body differ from those of theopening/closing chuck 10 according to the first embodiment.

As shown in FIGS. 10 and 12, each of the fingers 42 includes a pair oftrapezoidal overhanging portions 44 and 46 which project out laterallyfrom a main body portion 48 over the entire length thereof in thelongitudinal direction. Upper surfaces 44 a and 46 a and lower surfaces44 c and 46 c of each of the overhanging portions 44 and 46 are formedas tapered surfaces, which are inclined so as to come into closerproximity to each other toward side surfaces 44 b and 46 b. A guidegroove 50 of the body 12 includes a cross-sectional shape that conformsto the cross-sectional shape of the fingers 42. In order to enable thesliding movement of the fingers 42, the upper surfaces 44 a and 46 a,the side surfaces 44 b and 46 b, and the lower surfaces 44 c and 46 c ofthe respective overhanging portions 44 and 46 face toward the wallsurface of the guide groove 50 with a minute gap therebetween. Further,the bottom surface 48 c of the main body portion 48 also faces towardthe wall surface of the guide groove 50 with a minute gap therebetween.

Crowning is applied to the intersections between the five surfacesincluding the upper surfaces 44 a and 46 a, the side surfaces 44 b and46 b, the lower surfaces 44 c and 46 c, the first end surfaces 44 d and46 d, and the second end surfaces 44 e and 46 e that make up the outerperipheral surfaces of the respective overhanging portions 44 and 46.More specifically, crowning is applied to the intersections between theupper surfaces 44 a and 46 a and the first end surfaces 44 d and 46 d,to the intersections between the side surfaces 44 b and 46 b and thefirst end surfaces 44 d and 46 d, and to the intersections between thelower surfaces 44 c and 46 c and the first end surfaces 44 d and 46 d.Similarly, crowning is applied to the intersections between the uppersurfaces 44 a and 46 a and the second end surfaces 44 e and 46 e, to theintersections between the side surfaces 44 b and 46 b and the second endsurfaces 44 e and 46 e, and to the intersections between the lowersurfaces 44 c and 46 c and the second end surfaces 44 e and 46 e.Further, crowning is also applied to the intersections between the uppersurfaces 44 a and 46 a and the side surfaces 44 b and 46 b, and to theintersections between the lower surfaces 44 c and 46 c and the sidesurfaces 44 b and 46 b.

In these crownings, gaps are formed between the overhanging portions 44and 46 of the fingers 42 and the wall surfaces of the guide groove 50,in a manner so as to continuously and gently expand from portions whereboth members are in contact. Crowning that is applied to theintersection between the side surface 44 b and the upper surface 44 a ofthe overhanging portion 44 is shown in FIG. 11A. Crowning that isapplied to the intersection between the side surface 44 b and the lowersurface 44 c of the overhanging portion 44 is shown in FIG. 11B.

Further, in the guide groove 50 of the body 12, crowning is applied tothe intersections between the wall surfaces facing toward the uppersurfaces 44 a and 46 a of the overhanging portions 44 and 46 and thewall surfaces facing toward the side surfaces 48 a and 48 b of the mainbody portion 48. Furthermore, crowning is also applied to locationswhere stepped portions 50 a face toward the lower surfaces 44 c and 46 cof the overhanging portions 44 and 46.

In these crownings, gaps are formed between the overhanging portions 44and 46 of the fingers 42 and the wall surfaces of the guide groove 50,in a manner so as to continuously and gently expand from portions whereboth members are in contact. Crowning that is applied to theintersection between the wall surface of the guide groove 50 facingtoward the upper surface 44 a of the overhanging portion 44 and the wallsurface of the guide groove 50 facing toward the side surface 48 a ofthe main body portion 48 is shown in FIG. 11A. Crowning that is appliedto a location where the stepped portion 50 a faces toward the lowersurface 44 c of the overhanging portion 44 is shown in FIG. 11B.

In accordance with the opening/closing chuck 40 according to the presentembodiment, crowning is applied to the intersections between the fivesurfaces including the upper surfaces 44 a and 46 a, the side surfaces44 b and 46 b, the lower surfaces 44 c and 46 c, the first end surfaces44 d and 46 d, and the second end surfaces 44 e and 46 e that make upthe outer peripheral surfaces of the overhanging portions 44 and 46 ofthe fingers 42. Further, crowning is applied to a predetermined locationof the guide groove 50 of the body 12. Therefore, it is possible toalleviate concentration of stress when moments about the three axes orloads in a vertical direction act on the fingers.

Next, a description will be given with reference to FIGS. 12 and 13concerning a method (a crowning process) of applying crowning to thefingers 42. In this crowning process, using a third machining tool 52 (asingle machining tool) made up from a grindstone or an end mill,grinding is performed with respect to the side surfaces 44 b and 46 b ofthe pair of overhanging portions 44 and 46, grinding is simultaneouslyperformed with respect to the upper surfaces 44 a and 46 a and the lowersurfaces 44 c and 46 c of the pair of overhanging portions 44 and 46,and all of the aforementioned crowning is applied.

As shown in FIG. 12, the third machining tool 52, which is a rotatingbody, is made so that the shape of a surface thereof, which is incontact with the workpiece to be machined, matches the shapes of theupper surfaces 44 a and 46 a, the side surfaces 44 b and 46 b, and thelower surfaces 44 c and 46 c of the target overhanging portions 44 and46. The third machining tool 52 is arranged so that an axis thereof isarranged so as to be oriented along the Z direction, and can berotationally driven about such an axis. Further, the third machiningtool 52 is capable of being freely moved in the X direction and the Ydirection.

The third machining tool 52 has a first crowning machining portion 52 aand a second crowning machining portion 52 b. The first crowningmachining portion 52 a is a machining portion in order to apply crowningto intersections between the upper surfaces 44 a and 46 a and the sidesurfaces 44 b and 46 b of the overhanging portions 44 and 46. The secondcrowning machining portion 52 b is a machining portion in order to applycrowning to intersections between the lower surfaces 44 c and 46 c andthe side surfaces 44 b and 46 b of the overhanging portions 44 and 46.

When the crowning process is performed, first, the fingers 42 are fixedto the clamp base 38 in a posture in which the pair of overhangingportions 44 and 46 face upward. At this time, it is assumed that thethird machining tool 52 is at a position in confronting relation to theoverhanging portion 44 midway along the longitudinal direction (the Xdirection) of one of the overhanging portions 44.

Next, while being rotated about the axis thereof, the third machiningtool 52 is made to move in the Y2 direction and approach toward the oneof the overhanging portions 44, and is brought into contact at apredetermined pressure with the upper surface 44 a, the side surface 44b, and the lower surface 44 c. In accordance therewith, the uppersurface 44 a, the side surface 44 b, and the lower surface 44 c of theone of the overhanging portions 44 at a site where the third machiningtool 52 is placed in contact therewith are simultaneously subjected togrinding. In order to perform such grinding over the entirety of the oneof the overhanging portions 44 and the entirety of the other of theoverhanging portions 46, the third machining tool 52 is made to move ina circling manner around the outer sides thereof.

More specifically, as schematically shown in FIG. 13, the thirdmachining tool 52 is made to move in the X1 direction along the sidesurface 44 b etc. of the one of the overhanging portions 44 untilarriving in the vicinity of the first end surface 44 d. Thereafter, thethird machining tool 52 is moved in the Y2 direction until arriving inthe vicinity of the side surface 46 b of the other of the overhangingportions 46 while remaining at a distance from the finger 42.Furthermore, the third machining tool 52 is made to move in the X2direction along the side surface 46 b of the other of the overhangingportions 46 until arriving in the vicinity of the second end surface 46e. Next, the third machining tool 52 is moved in the Y1 direction untilarriving in the vicinity of the side surface 44 b of the one of theoverhanging portions 44 while remaining at a distance from the finger42. Thereafter, the third machining tool 52 is moved in the X1 directionalong the side surface 44 b or the like of the one of the overhangingportions 44 until being returned to its original position.

When the above-described third machining tool 52 is moved, regarding theone of the overhanging portions 44, crowning is applied to theintersection between the upper surface 44 a and the first end surface 44d, to the intersection between the side surface 44 b and the first endsurface 44 d, and to the intersection between the lower surface 44 c andthe first end surface 44 d. More specifically, at these intersections,grinding is performed while controlling the amount of traveling in theX1 direction and the amount of traveling in the Y2 direction of thethird machining tool 52 toward a target shape. Further, regarding theother of the overhanging portions 46, crowning is applied to theintersection between the upper surface 46 a and the first end surface 46d, to the intersection between the side surface 46 b and the first endsurface 46 d, and to the intersection between the lower surface 46 c andthe first end surface 46 d. More specifically, at these intersections,grinding is performed while controlling the amount of traveling in theX2 direction and the amount of traveling in the Y2 direction of thethird machining tool 52 toward a target shape.

Regarding the other of the overhanging portions 46, crowning is appliedto the intersection between the upper surface 46 a and the second endsurface 46 e, to the intersection between the side surface 46 b and thesecond end surface 46 e, and to the intersection between the lowersurface 46 c and the second end surface 46 e. More specifically, atthese intersections, grinding is performed while controlling the amountof traveling in the X2 direction and the amount of traveling in the Y1direction of the third machining tool 52 toward a target shape.Regarding the one of the overhanging portions 44, crowning is applied tothe intersection between the upper surface 44 a and the second endsurface 44 e, to the intersection between the side surface 44 b and thesecond end surface 44 e, and to the intersection between the lowersurface 44 c and the second end surface 44 e. More specifically, atthese intersections, grinding is performed while controlling the amountof traveling in the X1 direction and the amount of traveling in the Y1direction of the third machining tool 52 toward a target shape.

In this manner, merely by causing the third machining tool 52 to circleone time therearound, crowning can be applied to the intersections ofthe five surfaces that make up the outer peripheral surfaces of the pairof overhanging portions 44 and 46 of the fingers 42.

Third Embodiment

Next, a description will be given with reference to FIGS. 14 and 15concerning fingers 62 of an opening/closing chuck and a method ofmanufacturing the same according to a third embodiment of the presentinvention. The fingers 62 according to the third embodiment differ fromthe fingers 42 of the opening/closing chuck according to the secondembodiment, in that each of the overhanging portions includes a recessand a grease reservoir.

As shown in FIG. 14, one of the overhanging portions 64 includes arecess 72 centrally in the longitudinal direction of the upper surface64 a, the side surface 64 b, and the lower surface 64 c, and includescrowning regions CR1 and CR2 at both ends of the recess 72. A greasereservoir 70 opens in a bottom surface of the recess 72 that is formedin the upper surface 64 a. The other one of the overhanging portions 66also includes a similar grease reservoir 70 therein. Grease that isstored in the grease reservoirs 70 is supplied to the sliding surfacesof the overhanging portions 64 and 66, and the lubricating functionthereof is maintained.

Because the grease reservoir 70 opens on the bottom surface of therecess 72, an edge portion of the grease reservoir 70 does not come intocontact with the wall surface of the guide groove and causeconcentration of stress to occur. Further, the recess 72 is connected,via the crowning regions CR1 and CR2 to which crowning was applied, tosliding surfaces (surfaces in contact with the wall surfaces of theguide groove) on the upper surface 64 a, the side surface 64 b, and thelower surface 64 c. Therefore, due to the presence of the recess 72,concentration of stress within the guide groove does not occur.

Crowning is applied to the intersections between the five surfacesincluding the upper surfaces 64 a and 66 a, the side surfaces 64 b and66 b, the lower surfaces 64 c and 66 c, the first end surfaces 64 d and66 d, and the second end surfaces 64 e and 66 e that make up the outerperipheral surfaces of the respective overhanging portions 64 and 66.Further, in the guide groove of the body 12, crowning is applied to theintersections between the wall surfaces facing toward the upper surfaces64 a and 66 a of the overhanging portions 64 and 66 and the wallsurfaces facing toward the side surfaces 68 a and 68 b of the main bodyportion 68. Further, crowning is also applied to locations where thestepped portions of the guide groove face toward the lower surfaces 64 cand 66 c of the overhanging portions 64 and 66.

Next, a description will be given with reference to FIG. 15 concerning amethod (a crowning process) of applying crowning to the fingers 62. Inthis crowning process, using the third machining tool 52 (a singlemachining tool) also used in the second embodiment, grinding isperformed with respect to the side surfaces 64 b and 66 b of the pair ofoverhanging portions 64 and 66, grinding is simultaneously performedwith respect to the upper surfaces 64 a and 66 a and the lower surfaces64 c and 66 c of the pair of overhanging portions 64 and 66, applyingall of the aforementioned crowning.

While being rotated about the axis thereof, the third machining tool 52is brought into contact with the upper surface 64 a, the side surface 64b, and the lower surface 64 c at predetermined positions in thelongitudinal direction (the X direction) of the one of the overhangingportions 64, and these surfaces are simultaneously subjected togrinding. In order to perform such grinding over the entirety of the oneof the overhanging portions 64 and the entirety of the other of theoverhanging portions 66, the third machining tool 52 is made to move ina circling manner around the outer sides thereof.

When the third machining tool 52 is moved, at the intersection betweenthe side surface 64 b and the first end surface 64 d of the one of theoverhanging portions 64 and at the intersection between the side surface66 b and the first end surface 66 d of the other of the overhangingportions 66, similar to the case of the second embodiment, grinding isperformed while controlling the amount of traveling in the X directionand the amount of traveling in the Y direction of the third machiningtool 52 toward a target shape. At the intersection between the sidesurface 66 b and the second end surface 66 e of the other of theoverhanging portions 66, and at the intersection between the sidesurface 64 b and the second end surface 64 e of the one of theoverhanging portions 64 as well, similar to the case of the secondembodiment, grinding is performed while controlling the amount oftraveling in the X direction and the amount of traveling in the Ydirection of the third machining tool 52 toward a target shape.

Further, concerning the one of the overhanging portions 64, in order toform the crowning regions CR1 and CR2 and the recess 72 therein, in acentral vicinity in the longitudinal direction of the one of theoverhanging portions 64, grinding is performed while controlling theamount of traveling in the Y1 direction and the amount of traveling inthe Y2 direction of the third machining tool 52 toward a target shape.Similarly, in a central vicinity in the longitudinal direction of theother of the overhanging portions 66, grinding is performed whilecontrolling the amount of traveling in the Y1 direction and the amountof traveling in the Y2 direction of the third machining tool 52 toward atarget shape.

In this manner, merely by causing the third machining tool 52 to circleone time therearound, crowning can be applied to the intersections ofthe five surfaces that make up the outer peripheral surfaces of the pairof overhanging portions 64 and 66, together with enabling the crowningregions CR1 and CR2 and the recesses 72 to be formed on the pair ofoverhanging portions 64 and 66.

The present invention is not limited to the embodiments described above,but various configurations can be adopted therein without deviating fromthe essence and gist of the present invention.

What is claimed is:
 1. An opening/closing chuck comprising a pair offingers configured to slide inside of a guide groove of a body, andwhich are slidably supported in directions to approach toward andseparate away from each other; wherein the fingers each include a pairof overhanging portions configured to project out laterally from a mainbody portion, outer peripheral surfaces of the overhanging portions aremade up from five surfaces including upper surfaces, side surfaces,lower surfaces, first end surfaces, and second end surfaces, andcrowning is applied to intersections between these surfaces.
 2. Theopening/closing chuck according to claim 1, wherein the upper surfacesand the lower surfaces are perpendicular to the side surfaces.
 3. Theopening/closing chuck according to claim 1, wherein the upper surfacesand the lower surfaces are tapered surfaces configured to come intocloser proximity to each other toward the side surfaces.
 4. Theopening/closing chuck according to claim 1, wherein, in the guide grooveof the body, crowning is applied to an intersection between a wallsurface facing toward the upper surfaces and a wall surface facingtoward side surfaces of the main body portion.
 5. The opening/closingchuck according to claim 1, wherein crowning is applied to a locationwhere stepped portions in the guide groove face toward the lowersurfaces.
 6. The opening/closing chuck according to claim 3, wherein theoverhanging portions include recesses centrally in the longitudinaldirection of the upper surfaces, the side surfaces, and the lowersurfaces, together with crowning regions at both ends of the recesses,and grease reservoirs open on bottom surfaces of the recesses.
 7. Amethod of manufacturing a pair of fingers configured to slide inside ofa guide groove of a body of an opening/closing chuck, and which areslidably supported in directions to approach toward and separate awayfrom each other; wherein the fingers each include a pair of overhangingportions configured to project out laterally from a main body portion,and outer peripheral surfaces of the overhanging portions are made upfrom five surfaces including upper surfaces, side surfaces, lowersurfaces, first end surfaces, and second end surfaces, wherein the upperand lower surfaces are perpendicular to the side surfaces; the method ofmanufacturing the fingers comprising a step of applying crowning atintersections of the five surfaces, by a combination of performinggrinding with respect to the side surfaces by a first machining tool,and performing grinding with respect to the upper surfaces and the lowersurfaces by a second machining tool.
 8. A method of manufacturingfingers configured to slide inside of a guide groove of a body of anopening/closing chuck, and which are slidably supported in directions toapproach toward and separate away from each other; wherein the fingerseach include a pair of overhanging portions configured to project outlaterally from a main body portion, outer peripheral surfaces of theoverhanging portions are made up from five surfaces including uppersurfaces, side surfaces, lower surfaces, first end surfaces, and secondend surfaces, and the upper surfaces and the lower surfaces are taperedsurfaces configured to come into closer proximity to each other towardthe side surfaces; the method of manufacturing the fingers comprising astep of applying crowning at intersections of the five surfaces, byperforming grinding with respect to the side surfaces and simultaneouslyperforming grinding with respect to the upper surfaces and the lowersurfaces, using a single machining tool.
 9. The method of manufacturingthe fingers according to claim 8, wherein: the overhanging portionsinclude recesses centrally in the longitudinal direction of the uppersurfaces, the side surfaces, and the lower surfaces, together withcrowning regions at both ends of the recesses, and grease reservoirsopen on bottom surfaces of the recesses; and by the step, crowning ofthe crowning regions is applied.